The earth rotating, and I with it

A commission for the Science Museum in London

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This digital light dial reveals the earth spinning on its axis. It appears to trace the pendulum as it swings and slowly rotates. However, it is we and the dial that turn with the earth. This gives the illusion that the pendulum is rotating as it swings.

At the North Pole the pendulum would swing and rotate around a complete circle once every 24 hours, the time it takes the Earth to turn. At the equator the pendulum would swing but not appear to rotate. Between the poles and the equator the pendulum’s swing and the Earth’s rotation interact. In London this increases the pendulum’s rotation period to 30 hours and 30mins.

This pendulum is based on principles developed by physicist Léon Foucault in 1851. The suspension system, designed by Sir Brian Pippard in 1988, keeps the pendulum in constant motion.